The obligatory role of guanine nucleotide regulatory proteins (G proteins) in many transmembrane signalling events is now clearly established. While this has been elucidated most clearly for retinal phototransduction and for hormonal regulation of adenylate cyclase, similar mechanisms apparently are important for regulation of phospholipase C-catalyzed phosphoinositide hydrolysis, for neurotransmitter receptor-mediated modification of ion channel activity, for various secretory events, and for regulation of cell growth and differentiation. Although evidence for the involvement of a G- protein in most of these phenomena is strong, unambiguous identity of this protein has been established in only a few cases. The application of molecular cloning technology to studies of G-proteins in the last two years has resulted in the identification of new G-proteins, the function of which is not yet established. This symposium proposes to bring together leaders in the field of G-protein subunits and has resulted in the identification of new G-proteins, the function of which is not yet established. This symposium proposes to bring together leaders in the field of G-protein research. A major goal is to provide a forum for interaction between individuals who are actively studying G-protein function using model systems and investigators who are actively pursuing the identity and structure of G-proteins with technologies evolved from molecular cloning. The broad areas to be covered in the symposium include: 1) regulation of ion channels by G-proteins; 2) G-protein regulation of second messenger production; 3) receptors that interact with G-proteins; and 4) structure, function and expression of G-proteins. There will be five sessions total, one each on topics 1-3 and two sessions on topic 4. The meeting will also include a major keynote address and an afternoon poster session related to the general themes of the symposium. The published proceeding from the symposium are expected to make a timely and important contribution to this rapidly expanding field. This symposium will provide a unique opportunity to bring together biochemists, physiologists, pharmacologists, cell biologists, and molecular biologists who are the leaders in the multidisciplinary approach being taken in the field. The cross- fertilization and critical comparison possible in such an interaction should provide an important boost to our knowledge of G-protein structure/function.